A wide variety of medical devices utilized extruded polymeric members. For example, intravascular catheters and guide wires commonly utilize an extruded polymeric tube as a shaft component. Because intravascular catheters and guide wires must exhibit good torqueability, trackability and pushability, it is desirable that the extruded polymeric shaft component have good torque transmission, flexibility and column strength. These attributes are commonly incorporated into intravascular catheters by utilizing a composite shaft construction. Alternatively, the polymer material which forms the extruded polymeric shaft component may be oriented to enhance the mechanical characteristics thereof.
For example, U.S. Pat. No. 5,951,494 to Wang et al. discloses a variety of medical instruments, such as guide wires and catheters, formed at least in part of elongated polymer members having helical orientation. The helical orientation is established by post-processing an extruded elongate polymer member with tension, heat and twisting. Wang et al. theorize that the tension, heat and twisting process results in a polymer member that has helical orientation on the molecular level. Such molecular helical orientation enhances torque transmission of the elongate polymer member, which is important for some types of intravascular medical devices to navigate through tortuous vascular pathways.
U.S. Pat. No. 5,059,375 to Lindsay discloses an extrusion process for producing flexible kink resistant tubing having one or more spirally-reinforced sections. The extruder includes a rotatable member having an extrusion passageway for spirally extruding a thermoplastic filament into a base thermoplastic material to form a tube. The rotatable member is rotated to form the reinforcement filament in a spiral or helical pattern in the wall of the tubing.
U.S. Pat. No. 5,639,409 to Van Muiden discloses an extrusion process for manufacturing a tube-like extrusion profile by conveying a number of divided streams of material of at least two different compositions through a rotating molding nozzle. The streams of material flow together in the rotating molding nozzle to form at least two helically shaped bands of material. After allowing the combined streams of material to cool off, an extrusion profile comprising a plurality of bands of material extending in a helical pattern is formed.
U.S. Pat. No. 5,248,305 to Zdrahala discloses a method of manufacturing extruded catheters and other flexible plastic tubing with improved rotational and/or longitudinal stiffness. The tubing comprises a polymer material including liquid crystal polymer (LCP) fibrils extruded through a tube extrusion die while rotating the inner and outer die walls to provide circumferential shear to the extruded tube. Rotation of the inner and outer die walls orients the LCP in a helical manner to provide improved properties, including greater rotational stiffness.
Although each of these prior art methods provide some degree of orientation which enhances the mechanical characteristics of extruded polymeric members, there is an ongoing need to further enhance the mechanical characteristics of medical devices such as intravascular catheters and guide wires to improve performance thereof.